The Unknown Regions are a bunch of nonsense from the EU that doesn't fit with the setting as shown in the films.
1. I agree that Jocasta Nu's comment is foolish, arrogant, or both. It is nevertheless a statement with an acceptable margin of accuracy for a competent authority under the assumption that the Jedi Archives are reasonably complete for the galaxy far far away and its satellites, particularly given that the context is the question of the existence of a star system within or at least near the galaxy. The existence of any large volume of space which can reasonably be called the "Unknown Regions" in the immediate vicinity of the galaxy far far away would directly contradict that assumption, which would render Jocasta Nu's statement unacceptably-inaccurate to the point of being evidence for gross incompetence.And Jocasta Nu's comment has been considered incredibly moronic for years. The Yuuzhan Vong exist and they aren't in the records as are a great, great many things.
2. The Yuuzhan Vong are not from the immediate vicinity of the galaxy far far away - they're extraterrestrial invaders who have access to at least one form of FTL travel capable of speeds reasonably comparable to those of the hyperdrives used by the New Republic and Imperial Remnant, and apparently only began to make incursions into the old EU's "Known Regions" something like sixty years after the Old Republic fell. The standard hyperdrive of the setting, mind you, appears to be capable of crossing significant portions of the galaxy in a matter of hours - or less - within the Original and Prequel Trilogy films.
3. Unless they've been recanonized somewhere, the Yuuzhan Vong officially don't exist, because Disney de-canonized the old EU and the Sequel Trilogy - which makes no mention of them - occurs at about the time when the Yuuzhan Vong War was supposed to happen.